If you need to discuss sensitive information (legal strategy, business secrets, personal matters), assume a microphone could be present. But finding a tiny bug is hard. Sometimes, it's easier to defeat the bug than to find it.
Masking vs. Jamming
Jamming involves blasting powerful radio frequencies to block transmission. This is illegal in almost every country (including the US/FCC).
Masking (or Sound Masking) is legal. It involves generating noise in the same frequency range as human speech to "drown out" the conversation. To a microphone, your voice becomes mixed with the noise, making the recording unintelligible.
White Noise is Not Enough
Simple static (white noise) can be filtered out by modern AI software. To effectively mask speech, you need "babble noise"—a recording of multiple people talking at once. This confuses the microphone (and the AI) because it cannot distinguish your voice from the 10 other voices in the masking track.